As is well known in the art, tripod constant velocity joints have an outer member including a bottomed tubular cup-shaped portion with a shaft projecting from one end thereof, and an inner member positioned on and fixed to the distal end of a drive power transmitting shaft that is inserted in the outer member. The drive power transmitting shaft has splines (teeth) on a circumferential side wall thereof, and the inner member has a through hole defined therein, which has splines (teeth) on an inner wall thereof. When the distal end of the drive power transmitting shaft is inserted into the through hole, the splines mesh with each other, thereby joining the drive power transmitting shaft and the inner member to each other.
The distal end of the drive power transmitting shaft has an annular groove defined in a side wall thereof. A substantially C-shaped clip engages in the annular groove, which is exposed out of the through hole, thereby preventing the inner member from becoming dislodged from the drive power transmitting shaft (see, for example, Japanese Patent No. 2692030).
Japanese Patent No. 3626127 proposes that in order to prevent the inner member from becoming dislodged from the drive power transmitting shaft, annular grooves are defined both in the inner wall of the inner member and in the side wall of the drive power transmitting shaft. Also, a clip engages in the annular grooves, as is the case with a Birfield constant velocity joint.
The cup-shaped portion of the outer member has a plurality of (generally, three) track grooves defined in an inner wall thereof, and the inner member has trunnions projecting from a side wall of a ring-shaped annular portion.
The trunnions extend toward the track grooves. Roller members are rotatably held in engagement with the respective trunnions by rolling members such as needle bearings or the like, and the roller members are slidably inserted in the track grooves.
The tripod constant velocity joint of the above structure is generally assembled manually by a worker in the following manner. First, the worker brings the splines of the inner member into mesh with the splines on the distal end of the drive power transmitting shaft. Thereafter, the worker places the roller members on the respective trunnions with the rolling members held on the inner walls thereof, and inserts the roller members into the track grooves of the outer member.
It is tedious and time-consuming, and not of good working efficiency, for the worker to assemble the tripod constant velocity joint manually. In view of this drawback, there has been a demand for an assembly apparatus for automatically assembling a tripod constant velocity joint. For example, Japanese Laid-Open Patent Publication No. 06-312326 proposes an assembly apparatus, which is focused on the timing required to fill a cup-shaped portion with grease.
According to the assembly apparatus disclosed in Japanese Laid-Open Patent Publication No. 06-312326, as can be understood from FIGS. 7 and 8 thereof, an inner member including roller members mounted on trunnions and a joint boot are installed on the distal end of a drive power transmitting shaft, and then the roller members are inserted into track grooves provided in a cup-shaped portion, thereby assembling the tripod constant velocity joint. If the inner member including the roller members mounted on the trunnions is inserted beforehand in the cup-shaped portion, and then the drive power transmitting shaft is passed through a through hole of the inner member, then a clip needs to be shrunk and passed through the through hole of the inner member, irrespective of whether the clip engages in the annular groove of the drive power transmitting shaft, which is exposed outside of the through hole of the inner member, as disclosed in Japanese Patent No. 2692030, or whether the clip engages both in the annular groove provided in the inner wall of the through hole of the inner member, and in the annular groove of the drive power transmitting shaft, as disclosed in Japanese Patent No. 3626127. Unless the clip is shrunk, the clip cannot pass through the through hole.
In other words, the assembly apparatus disclosed in Japanese Laid-Open Patent Publication No. 06-312326 is capable only of automating a process of housing the inner member mounted on the drive power transmitting shaft in the cup-shaped portion, but is unable to automate the process of installing the inner member on the drive power transmitting shaft.
In order to shrink the clip, it may be necessary to employ a shrinker, which has been used in the assembly of Birfield constant velocity joints. However, such a shrinker fails to reach into deep areas of the track grooves, because the track grooves tend to be long in a tripod constant velocity joint. Consequently, it is highly difficult to shrink the clip automatically.